This application claims the benefit of priority of German Patent Application No. 19913919.9, filed on Mar. 26, 1999, which is incorporated by reference herein in its entirety.
The present invention relates to a data transmission system in a motor vehicle that is equipped with batteries generating two different voltages (e.g., 12 V and 42 V), and hence with two on-board power supply networks.
An example of such an on-board power supply network architecture is described in VDI Berichte No. 1287 (1996), pages 295 to 317.
Conventionally, a data connection is necessary between functionally cooperating on-board apparatuses, such as between control apparatuses or between a control apparatus and corresponding sensors and/or actuators (e.g., immobilizer control systems and corresponding components, entry control systems, passenger protection systems, and the like). The data connection is usually achieved through a data bus connected to the on-board apparatuses.
German Patent No. 197 33 866 discloses a data transmission method. A satellite station is supplied with energy from a central station through a common transmission line for data transmission and power supply. For the transmission of energy and data, however, only one line is used (the data transmission line). Such a data transmission method is very sensitive to error.
The present invention addresses the problem of creating a communication system that will permit reliable data communication even if errors occur.
The present invention provides a data communication system for a vehicle. The system comprises a first voltage supply line at a first voltage relative to ground; a second voltage supply line at a second voltage relative to ground; a first electronic apparatus connected to the first and second voltage supply lines; and a second electronic apparatus connected to the first and second voltage supply lines. The first electronic apparatus is adapted to transmit a first set of the data over the first and second voltage supply lines, and the second electronic apparatus adapted to receive the first set of data over the first and second voltage supply lines.
The present invention further provides a method of communicating data for a vehicle. The vehicle has a first battery supplying a first voltage to a first on-board power supply network and a second battery supplying a second voltage to a second on board power supply network. The first voltage nominally is greater than the second voltage. The method comprises connecting a first electronic apparatus to the first and second on-board power supply networks; connecting a second electronic apparatus to the first and second on-board power supply networks; transmitting the data from the first electronic apparatus over the first and second on-board power supply networks; and receiving the data at the second electronic apparatus from the first and second on-board power supply networks.
In a motor vehicle communication system according to the present invention, transmitted data is carried in parallel through two sets of voltage supply lines (one for each of the batteries). Consequently, the advantages of the present invention include eliminating a separate data bus and providing a redundant design, i.e., reliable data communication is sustained through one of the voltage supply lines if the other voltage supply line fails due to a defect or short circuit, for example.
Frequency filters (e.g., high-pass filters or preferably band-pass filters tuned to the data transmission frequencies) are provided for coupling and decoupling the data to and from the voltage supply lines, and for isolating the data from the direct current carried by the voltage supply lines. Thus, a sufficiently great signal-to-noise ratio is assured, as well as good isolation from the direct current.
Data can be transmitted directly to the voltage supply lines as a series of bits. Alternatively, each communication apparatus can be equipped with a modulator sending signals and with a demodulator for receiving signals. Of course, the modulator and demodulator can be combined to form a modem. However, a communication apparatus that is designed only for sending or receiving signals, a modulator or demodulator, respectively, is sufficient for such apparatus. Thus, data can be converted to or from a disturbance-free transmittable frequency range. The modems can be of conventional design, such as those used in analog telephony.
During the sending procedure, modulated data to be transmitted can be put into both voltage supply lines simultaneously. However, in the reception procedure, a receiver input can be connected selectively by a switch to only one voltage supply line so as to avoid interference between modulation signals that are shifted out of phase between the two voltage supply lines, but are otherwise identical. For example, if the receiver recognizes that no data is being delivered, the switch can then select the other voltage supply line. The switch can also be operated cyclically or non-cyclically in order to determine which voltage supply line can provide a better signal.
At least one line coupler can be provided between the two voltage supply lines. For example, the line coupler can be a band-pass filter tuned to the data transmission frequencies or modulation signal frequencies. This assures that data or modulation signals transmitted on the one voltage supply line are also conducted by the other voltage supply line, even though the apparatus is directly transmitting data on only one voltage supply line, either by choice or due to interference.
The current for operating the connected electronic apparatus can be provided from either or both voltage supply lines through a common connection to the input of the electronic apparatus. To separation different potentials between the voltage supply lines, decoupling devices (e.g., diodes), can be used. If one voltage supply line is not operational due to a short circuit or other defect, power can be supplied to the electronic apparatus from the other of the two voltage supply lines, thereby assuring that the required direct current remains unvaried. Thus, interference, losses, interruptions, short circuits, and other factors disturbing a voltage supply line do not impair the functionality of the connected electronic apparatus, since their power supply and data communications (sending and/or receiving of data as well as internal data processing) and other ways of operation are sustained to the full extent by the other voltage supply line.
The data transmission method of the invention is likewise characterized by the advantages and operating features explained above.